You are wrong. Deck 6 of the dinning room is specifically set for two seatings.
OP, I looked on my app for the 4/6 sailing and there are NO seatings available but I think I remember that it's 5:30 and 7:30. I, too, found it odd that they went back to the traditional seating. It's also the largest of the three dinning room areas. I am so surprised that so many people want that way of having dinner.